1. Field of the Invention
The present invention relates to a system and method for monitoring operation of a press assembly.
2. Background Art
Because of the high impact, high force loading conditions present in some stamping press operations, various mechanical elements of the press may be prone to premature failure. For example, if it is estimated that a press will have a life span of five years based on certain production levels of stamped parts, and one or more of the press components fails after only one or two years, the components will have failed prematurely; this may result in significant downtime and lost revenue. Premature failure of press components may be particularly prevalent when an older press is reconfigured to perform stamping operations subject to impacts greater than those considered in the original design parameters.
FIG. 1 shows an example of a double action press 10 of the type that has been used in the stamping industry for many years. The press 10 includes a crown 12 and a press bed 14 supported on a foundation 16. The press 10 is known as a double action press because a blank holder slide 18 is moved downward in a first action, carrying with it an upper portion 20 of a blank holder 22. The upper portion 20 of the blank holder 22 captures a workpiece 24 between it and a lower portion 26 of the blank holder 22.
As shown in FIG. 1, the lower portion 26 of the blank holder 22 is firmly attached to the press bed 14 so there is little impact when the upper portion 20 engages the workpiece 24. After the workpiece 24 is securely clamped between the upper and lower portions 20, 26 of the blank holder 22, a drawing slide 28 is actuated and moved downward, carrying with it a portion of a die, or upper shoe 30. The upper shoe 30 contacts the workpiece 24, drawing it into another portion of the die, or lower shoe 32. Again, the impact of this action is not very high, since the movement is just the upper shoe 30 drawing the already fixed workpiece 24 into the lower shoe 32.
Attached to the crown 12 is a toggle drive system 34 made up of flywheels, gears, and other elements for which the labels have been removed in FIG. 1 for clarity. A slide connecting rod 36 connects the toggle drive 34 with the drawing slide 28. Similarly, a blank holder connecting rod 38 connects the toggle drive 34 with the blank holder slide 18. A motor 40, shown in phantom in FIG. 1, may be used to provide mechanical power to the toggle drive 34.
When the press 10 is operated as a double action press as shown in FIG. 1, the elements of the press 10 may each have an actual life span that generally coincides with its expected life span. One disadvantage of the configuration of the press 10 is that the orientation of the workpiece 24 may be upside down with respect to additional operations that need to be performed. Therefore, as explained in more detail below, double action presses, such as the press 10, may be reconfigured as a single action press with a reversed orientation for the workpiece. Although this facilitates faster transfers and additional operations on the workpiece, it may also result in higher impacts and premature failure for the press components.
Therefore, a need exists for a system and method for monitoring operation of a press to provide information related to the expected life span of the press components. This information can be used, for example, to alter operation of the press such that the press components will have actual life spans generally in accordance with their expected life spans, or conversely, can allow a production manager to predict component failure and perform preventative maintenance according to a planned schedule, rather than repairing and replacing failed components during an unexpected breakdown.